Tridymite is a high-temperature polymorph of
quartzand usually occurs as minute tabular white or colorless pseudo-hexagonal tricliniccrystals, or scales, in cavities in acidic volcanic rocks. Its chemical formulais SiO2. Tridymite is stable between 870 and 1470 degrees Celsius. It has a Mohs hardnessof 6.5 to 7, a specific gravity of 2.28 to 2.33 and refractive indices of nα=1.471 - 1.482 nβ=1.472 - 1.483 nγ=1.474 - 1.488. Optically, tridymite has a birefringence of < .004 and has a 2V between 40 and 90 degrees, it may have wedge, complex or polysynthetic twinning.
Tridymite was first described in 1868 and the type location is in Hidalgo,
Mexico. The name is from the Greek "Tridymos" for "triplet" as tridymite commonly occurs as twinned crystal "trillings".
* [http://www.mindat.org/min-4015.html Mindat]
* [http://webmineral.com/data/Tridymite.shtml Webmineral]
* [http://mineral.galleries.com/minerals/silicate/tridymit/tridymit.htm Mineral galleries]
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Tridymite — Catégorie IX : silicates Tridymite Ochtendung, Eifel, Allemagne … Wikipédia en Français
Tridymite — Trid y*mite, n. [Gr. ? threefold. So called in allusion to the supposed threefold nature of the twin crystals.] (Min.) Pure silica, like quartz, but crystallizing in hexagonal tables. It is found in trachyte and similar rocks. [1913 Webster] … The Collaborative International Dictionary of English
tridymite — ● tridymite nom féminin Silice cristallisée dans le système orthorhombique, pseudohexagonale, que l on trouve dans certaines roches volcaniques … Encyclopédie Universelle
tridymite — /trid euh muyt /, n. Mineral. a polymorph of quartz occurring in the form of small crystals, commonly twinned, in siliceous volcanic rocks. [1865 70; < G Tridymit, equiv. to tridym (Gk trídym(os) triple, equiv. to tri TRI + (dí)dymos DIDYMOUS) +… … Universalium
tridymite — noun A rare mineral of volcanic rocks that solidified at a high temperature, with the chemical composition silicon dioxide, SiO. Tridymite is chemically identical to quartz, but has a different crystal structure. Sometimes contains sodium… … Wiktionary
tridymite — tridimitas statusas T sritis chemija apibrėžtis Polimorfinė SiO₂ atmaina. atitikmenys: angl. tridymite rus. тридимит … Chemijos terminų aiškinamasis žodynas
tridymite — A form of silica used in dental casting investment. [fr. G. tridymos, threefold] … Medical dictionary
tridymite — [ trɪdɪmʌɪt] noun a high temperature form of quartz found as thin hexagonal crystals in some igneous rocks and stony meteorites. Origin C19: from Ger. Tridymit, from Gk tridumos threefold , because it occurs in groups of three crystals … English new terms dictionary
tridymite — trid·y·mite … English syllables
tridymite — n. a crystallized form of silica, occurring in cavities of volcanic rocks. Etymology: G Tridymit f. Gk tridumos threefold (as TRI , didumos twin), from its occurrence in groups of three crystals … Useful english dictionary